Noting that "alcohol use is frequently implicated as a factor in non-adherence to highly active antiretroviral therapy (HAART)," the study authors performed a meta-analysis to provide a quantitative evaluation of the association between alcohol use and adherence by aggregating findings across studies and examining potential moderators.

Literature reviews identified 40 qualifying studies involving over 25,000 participants. The researchers then coded the studies on several methodological variables.

The combined analysis showed alcohol drinkers were approximately 50-60 percent as likely to be classified as adherent (odds ratio [OR]=0.548, 95 percent confidence interval [CI]:0.490 to 0.612) compared with abstainers (or those who drank relatively less). Effect sizes for problem drinking, defined as meeting the National Institute on Alcohol Abuse and Alcoholism criteria for at-risk drinking or criteria for an alcohol use disorder, were greater (OR=0.474, 95 percent CI=0.408 to 0.550) than those reflecting any or global drinking (OR=0.604, 95 percent CI=0.531 to 0.687). Several variables moderated the alcohol-adherence association.

The study results suggest a significant and reliable association of alcohol use and medication non-adherence, the researchers concluded. "Methodological variables seem to moderate this association and could contribute to inconsistent findings across studies. Future research would benefit from efforts to characterize theoretical mechanisms and mediators and moderators of the alcohol-adherence association."